跟踪类别的 SKNodes

Question

我有一个函数可以将敌人添加到我的场景中，该函数会按时间间隔调用

我如何跟踪场景中的敌人数量以限制我在每个关卡中的敌人数量？

**在我的更新函数中**

CFTimeInterval timeSinceLastEnemy = currentTime - self.lastEnemyUpdateTime;
self.lastEnemyUpdateTime = currentTime;
if (timeSinceLastEnemy > 1) { // more than a second since last update
    timeSinceLastEnemy = 1.0 / 60.0;
    self.lastEnemyUpdateTime = currentTime;
}

[self spwanEnemyWithTime:timeSinceLastEnemy];

**计时器和添加敌人的方法**

- (void)spwanEnemyWithTime:(CFTimeInterval)timeSinceLast {

    self.lastEnemySpawn += timeSinceLast;
    if (self.lastEnemySpawn > 0.6) {
        self.lastEnemySpawn = 0;
        [self spawnEnemy];
    }
}

-(void) spawnEnemy {

    SKSpriteNode *enemy = [SKSpriteNode spriteNodeWithImageNamed: enemySprite];

    int minX = 5;
    int maxX = self.frame.size.width;
    int rangeX = maxX - minX;
    int actualX = (arc4random() % rangeX) + minX;

    // Create the enemy slightly off-screen along the upper edge,

    enemy.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:CGSizeMake(enemy.size.height - 10 , enemy.size.width)]; 
    enemy.physicsBody.dynamic = YES;
    enemy.physicsBody.categoryBitMask = enemyCategory; 
    enemy.physicsBody.contactTestBitMask = bulletCategory; 
    enemy.physicsBody.collisionBitMask = 0;     

    // and along a random position along the X axis as calculated above
    enemy.position = CGPointMake(actualX, self.frame.size.height + enemy.size.height);
    [self addChild:enemy];
    enemy.xScale = 0.2;
    enemy.yScale = 0.2;
    enemy.zPosition = 4;

    // Create the actions
    SKAction * actionMove = [SKAction moveToY:(0 - enemy.size.height) duration:4];
    SKAction * actionMoveDone = [SKAction removeFromParent];
    [enemy runAction:[SKAction sequence:@[actionMove, actionMoveDone]]];
}

Answer 1

我承认我无法理解你用双计时器做什么，所以我假设这部分工作如你所愿。对于敌人的数量，这难道不能像在你的 spawnEnemy 上增加一个计数器并在敌人从场景中移除自己时减少计数器一样简单吗？

你必须仔细检查我的 Obj-c，我已经有一段时间没有使用它了。

int enemyCount = 0;

-(void) spawnEnemy {

    enemyCount += 1

    ...

    // Create the actions
    SKAction *actionMove = [SKAction moveToY:(0 - enemy.size.height) duration:4];
    SKAction *actionMoveDone = [SKAction removeFromParent];
    SKAction *decrementCount = [SKAction runBlock: ^(void) {
        enemyCount -= 1;                           
    }];

    [enemy runAction:[SKAction sequence:@[actionMove, actionMoveDone, decrementCount]]];
}

仅供参考，您的方法有错别字 "spwanEnemyWithTime"

跟踪类别的 SKNodes

Keeping track of SKNodes for a category

ios

objective-c

sprite-kit

skspritenode